Method of packaging



Sept. 5, 1933. C.J. sTAuD El AL METHOD OF PACKAGING Filed Oct. 12, 1931Cellulasip .bwse shee Cellulosio 112m sheet @rilJsb dmlf Patented Sept.5, .1933

UNITED STA METHOD ,0! PAOKAGIN G Cyril I. Stand and William 0. Kenyon,Rochester,

N. 1., aleignors to Eastman Kodak Company, Itochester, N. 1., acorporation of New York Application Octobm 1:, 1m. Serial No. scam'icclum.

This invention relates to the art of packaging and more particularly toan improved method of making a wide variety of containers includingcigar wrappers, food packages and the like.

5 The invention relates specifically to a method of making packages froma new water resistant type of thin cellulosic sheeting having anovercoating of gum and wax, wherein the required seams, joints, andclosures are formed in a novelmanner.

It is highly important in the manufacture of this type of container thatthe sides, ends, and other parts thereof should be securely closed andsealed by means of joints capable of withstanding the various strainsand stresses to which they are subjected in the ordinary course offilling, packing, and transporting. A good example of this type ofcontainer is the common transparent package for displaying nuts, candiesand other edibles in drug stores.

This type of package may be formed by folding a sheet of transparentmaterial, such as wax paper, viscose, or the material sold under thename Cellophane," and consisting primarily of regenerated cellulose,into the desired form and cementing the edges together by treating themwith an adhesive and applying heat and pressure. After the contents havebeen inserted in the package, the opening at the top is sealed insubstantially the same manner. It is customary to reinforce the jointsby making a double fold before applying the adhesive.

Various methods of closing the sides or ends of these containers havebeen proposed, the most common method being by applying a cement oradhesive to the edge portions and simply pressing them together.

When sealing cellulosic sheeting, the cement generally contains a base,such as pyroxylin, cel- 40 lulose acetate, and various other ingredientswhich are dissolved in an appropriate solvent. Another method is tosimply bring the edges of the material together and apply heat andpressure, so that a certain amount of fusion of the sheet materialitself takes place.

In dealing with a new type of cellulosic material having a waterresistant overcoating, it has been proposed to form the seals or jointsof containers by simple fusion of the respective overcoating layers ofthe sheet by application of heat and pressure. A still further method isto treat the desired portions of the coated sheet with a solvent whichdissolves the overcoating layers and causes them to run together. Upon.

duced consisting of-the co-mingled portions of the overcoating layerswith the result that is held 'together solely by the adhesive bond ofwater proofing material.

The present invention is distinguished from the above mentionedpackaging operations by the fact that containers are made from a new andimproved type of waterproof cellulosic sheeting having a gum-waxmoistureprooilng overcoating and in the further fact'that the joints orseals are produced by a simple and unique method in which reliance isplaced, neither upon the use of adhesive, nor upon fusion of therespective waterproof coatings alone. Our invention is particularlycharacterized by the use of 7 special solvent sealing agents whichaffect both the waterproofing layer and the adjacent underlying portionof the base sheet, causing" them toalcoalesce to produce a very strong,transparent 8e 5 The invention therefore has an object to im- 7 proveupon known methods of making containers by provision of a process inwhich the use of known adhesives is eliminated. A furtherv object is toprovide a method of making packages 30 from a new type of waterproofcellulosic sheeting having a gum-wax water resistant overcoating. Astill further object is to provide a method of sealing packages orcontainers by the use of solvents or solvent sealing agents which 3:;effect the base sheet in addition to effecting the waterproofingmaterial. Other objects will appear hereinafter.

These objects are accomplished by the following invention which will nowbe described with reference to several of its preferred embodimentswhich are included merely for purposes of illustration and not as alimitation.

Briefly stated, the process comprises folding or otherwise shaping awaterproof sheet of cellulosic material into a package or container ofthe desired form and'then sealing the ends and edges by application of asolvent sealing agent which exerts both a solvent action on theovercoating of the sheet and a swelling or solvent action of theadjacent underlying portions of the base sheet itself. Upon application.of pressure preferably with heat, the overcoating material and thedissolved'or swollen portions of 5 the base sheet coalesce at the pointswhere they are brought together to produce a strong adhesive seal ofgreat toughness and strength.

Our novel method of packaging or forming containers will be betterunderstood by refercellulosic material ence to the accompanying drawingin which like reference numerals refer to like parts.

Fig. 1 is a cross section through a sheet of cellulosic material havinga water resistant gumwax overcoating, the thickness of both base sheetand. overcoating layer being greatly exaggerated and the relativethickness of each layer. being out of true proportion in order to moreclearly bring out the characteristic features of the material.

Fig. 2 is a sectional view illustrating one method of forming a sealedjoint according to the invention.

Fig. 3 is another sectional view illustrating a slightly different typeof operation in which the edges of the material are folded over uponthemselves to form a reinforced joint.

Fig. 4 is a perspective view of a sealed package made according to theinvention.

Fig. 5 is a sectional view along the line 5-5 of Fig. 4 showing onemethod of forming a lap joint and sealing the package after the contentshave been inserted.

Fig. 6 illustrates the general method of forming lap joints, or ofbuilding up a laminated structure by this method.

Fig. 7 is a cross sectional view through a sealed joint illustrating theformation of the bond holding the two sheets together and consisting ofco-mingled portions of base sheet and moisture-proof coating.

Fig. 8 is a cross section through a sheet of having a water-resistantcoating comprising separate layer of gum and wax, the thickness of bothbase sheet and overcoating being greatly exaggerated for convenience ofillustration.

In one form of carrying our invention into practice a moisture-proofsheet of cellulose acetate may be prepared according to the methoddescribed in the co-pending application of Norman F. Beach and Bruce E.Gramkee, Serial No. 551,491, filed July 17, 1931, in which a mixture ofgum and wax is applied to the base sheet to form a water-resistantlayer, or the sheeting may be prepared according to the method describedin the copending application of Norman F. Beach and James G. McNally,Serial No. 551,490, filed July 17, 1931, in which the water resistantcoating consists of separate layers of gum and wax. The sheet is foldedor otherwise formed into the desired shape and the edge portions aretreated with a solvent sealing agent which will be more particularlydescribed hereinafter.

As shown in Fig. 2, these treated edges which are softened by the actionof the sealing agent on the overcoating layer and upon the adjacentunderlying portionsof the base sheet,'are then brought together andsubjected to heat and pressure between the heated pressure devices 3.The solvent is evaporated off and both moisture resistant overcoatinglayers and portions of the base sheet material merge or coalesce to formthe joint. The pressure de vices may be provided with any conventionalform of heating unit, such as electrical resistances or steam coilswhich are generally illustrated in Fig. 2 by the numeral 4.

Another slightly different method of forming the joints is to bring thetreated edges of the sheet together and fold the material upon itself toform a reinforced joint 5 illustrated in Fig. 3. As in the previouslydescribed method, the edge portions of the material are treated with thesolvent sealing agent and the 'sheet is folded and Loaasob subjected toheat and pressure between the elements 3.

In Figs. 5 and 6 is shown a method of forming a lap joint. In this casethe edges are treated with a solvent sealing agent and brought togetheras shown and placed in contact with the elements 3, whereupon thesolvent is evaporated oil and a strong sealed joint is produced. Themethod illustrated in Fig. 5 may be conveniently used for sealing apackage after the contents have been inserted therein.

In Fig. 4 is shown a container 6 in which the contents have been sealed.In this particular type the ends have been sealed by forming a lapJoint, but it will be evident that a joint such as that shown in Figs. 2and 3 may be used for this purpose if desired.

We have experimented with many different solvent sealing compounds andhave determined the properties which they must possess in order to besuccessfully applied to coated or uncoated cellulosic sheeting toproduce the desired sealing or bonding effect and to make strong,smooth, transparent joints free from blisters and wrinkles. In thefollowing description and claims we shall refer to these substances assealing agents or sealing adhesives and intend to include within thescope of these terms all of those materials which produce the resultsconstituting our invention.

We have found that the sealing agent should have a solvent or swellingaction on the cellulosic base, since it is the coalescing of limitedportions of the base sheets making up the joints that broadlycharacterizes our invention and makes possible our greatly improvedresults.

When forming joints or seals with a moistureproof cellulose sheetinghaving a gum-wax overcoating, it is desirable that the sealing agenthave a solvent action on the coating in order to provide for penetrationof this waterproofing layer by the solvent and for the dissolving orswelling of portions of the underlying cellulosic material. If thesolvent sealing agent is not inherently a good wax solvent its solventproperties for wax may be enhanced by the addition of certainhydrocarbons, such as gasoline, parafiine, or benzene.

The sealing agent may have either a solvent or a swelling action on thematerial of the base sheet. In any event, the desired effect is to bringthe surface of the cellulose acetate, for example, into a conditionwhereby portions of the contacting sheets will merge or coalesce andenter into and form a part of the adhesive bond. This result will beaccomplished if the sealing agent has a solvent effect on the celluloseacetate, since the surfaces will be softened and partially dissolved, inwhich condition they will readily flow together upon contact.Evaporation of the solvent under heat and pressure leaves the contactingportions of the respective sheets intimately co-mingled.' A somewhatsimilar action takes place when thesealing compound acts principally asa swelling agent since, upon application of pressure, the swollenportions of the sheets are effectively co-mingled. In the case ofswelling, the solvent has a tendency to diffuse into the celluloseacetate base rather than to dissolve it in the ordinary sense of theword,

I but the ultimate result is the same as far as the co-mingling of thematerial is concerned.

These agents, when used alone, should preferably not have too great asolvent action on the base sheet for the reason that this will weakenthe material and, if excessive, may even give those of low acetylcontent, are soluble in ho rise to tearing or perforation. Acetone maybe mixtures of ethyl alcohol and toluene and it is cited. as an exampleof an agent which has too great a solvent power for cellulose acetatesheeting and is for this reason unsuitable for solvent sealing of thismaterial. It will be apparent from the following discussion of severalclasses of typical solvents or sealing agents-that they may varyconsiderably in their solvent properties with respect to gum or wax, andalso with respect to their solvent or swelling action on the material ofthe base sheets. Some compounds may have a greater solventpower for gumthan others. In like manner, they may differ with respect to theirsolvent or swelling action on the base sheet. It should be noted in thisconnection that these agents may also vary considerably in the solventand swelling effect they produce upon different types of cellulosic basesheet materials. For example, when using a cellulose acetate base thiseffect will vary somewhat with the degree of acetylation of thecellulose and the sealing agent should. accordingly, be selected withrelerence to the particular type of cellulose acetate dealt with.

When applying the solvent sealing agents to cellulosic sheet materialwhich has a moistureproof overcoating of gum and wax, they should bemixed or dissolved in a diluent such as a liquid aliphatic or aromatichydrocarbon, in order to insure a solvent action upon the overcoatinglayer and further provide for the penetration of this layer by theagent. When adding these hydrocarbon diluents to solvent. sealingagents, the capacity of the latter for dissolving the base sheetmaterial is considerably reduced.

In some cases this solvent power is reduced to such an extent that thesealing agent merely diffuses into the sheet without exerting anypronounced action thereon.

We have also found that various combinations of solvents may be usedeffectively, although it will be necessary to select the ingredientsentering into the combination with respect to the specific effects to beproduced on the material dealt with, both as regards the character ofthe base sheet and the nature of the gum-wax overcoating.

We have found that alcohols of both the aromatic and aliphatic seriescontaining one or more hydroxyl groups are especially satisfactory,effective sealing agents. Typical examples of such alcohols are methyl,ethyl and n-butyl alcohols, glycerol, benzyl alcohol, and Cyclohexanol.In this series, both methyl and ethyl alcohol produce a swelling actionon cellulose acetate and, at high temperatures, methyl alcohol has agreater tendency in this direction than does ethyl. In'

general, it may be said that the amount of swelling produced decreasesin the saturated aliphatic alcohols as the molecular weight increases.The compounds have a pronounced solvent action upon the gum ingredientof the overcoating. In the case of polyhydric alcohols of which glycerolis an example, the gum is dissolved and the cellulose acetate basematerial is somewhat swollen. Both of these classes of compounds may bediluted by the addition of saturated hydrocarbons of the aliphaticseries or of toluene or other saturated hydrocarbons of the aromaticseries. The use of these diluents tends to increase the solvent power ofthe sealing agent for the paraffin-wax component of the moistureprooflayer, and, apparently, does not seriously impair the solvent powerwhich the agent has for the gum component.

Some types of cellulose acetate, particularly therefore necessary inusing a mixed solvent of this character to regulate the ingredientsentering into its composition, as well as the temperatures, so that thesolvent action will not be carried to an undesirable extent.

With respect to benzyl alcohol, this compound is a solvent for gum, butdoes not appreciably affect paraflin. It is a solvent for a considerablevariety of cellulose acetates, and its use as a sealing agent must becarefully controlled in order that its solvent power does not producethe above-mentioned undesirable effects. The use of benzyl alcoholdissolved in toluene results in a more ready solution of themoistureproof layer and moderates the solution tendency of the benzylalcohol to more nearly that of high dilatancy or swelling in thecellulose acetate layers.

Cyclohexanol is a solvent for ester gum, a nonsolvent for paraffin, anda good swelling agent for cellulose acetate. The addition of toluene tothis compound decreases its swelling tendency slightly at moderateconcentrations.

As regards the temperature at which these compounds are used, it may besaid that in the case of the aliphatic alcohols the temperature may beincreased without the formation of blisters as the length of the carbonchain of the alcohol increases.

The control of temperature is something which is governed very largelyby the boiling point of the particular compound employed and it has beenfound that the more satisfactory joints or seals are produced at thelower temperatures, providing they are high enough to provide for properevaporation of the solvent. High temperatures have a tendency to produceblistering with a resulting unsatisfactory appearance of the finishedproduct.

Wehave also found that esters of monohydric and polyhydric alcohols canbe used effectively to unite moistureproof cellulose acetate sheeting ofthe general character under consideration. For example, ethyl acetate,monoacetin, and diacetin, are capable of causing this union and theirresulting seams are very smooth and free from blisters. It should benoted that the lower boiling esters have a tendency to produce someblistering,,whereas those of high boiling point do not, under the sameconditions of temperature. Among these esters, ethyl acetate has beenfound to be a good solvent for ester gum, for example, but is not asolvent for a wax such as paraffin, and, while it dissolves only certaintypes of cellulose acetate, it is a powerful swelling agent for a greatvariety of them. Methyl acetate, on the other hand, will dissolvecellulose acetate having a wide range of acetyl content. Propyl andbutyl acetates produce swelling of the cellulose acetate base sheet indecreasing amounts. Monoacetin is a solvent for ester gum, a non-solventfor parailln, and a swelling agent for cellulose acetate. The samestatement applies to diacetin. Glycol diacetate has the same propertieswith respect to gum and wax and is, at the same time, a solvent for agreat variety of cellulose acetates having between 36 and 40% acetylcontent.

Additional sealing agents are the keto alcohols,

, a typical example of which is diacetone alcohol.

This compound is a solvent for ester gum, a nonsolvent for paraflin, anddissolves a wide variety of cellulose acetates. Benzoin has the sameproperties with respect to gum and wax and it is a solvent for celluloseacetate at relatively high ingredients.

temperatures. This material, which is a solid at ordinary temperaturesand melts at 137 0., may be applied either in a melted condition orby'solution in tolueneor cyclohexanol, the volatile material beingpreferably evaporated before the application of heat and pressure. As inthe case of the alcohols discussed above, when toluene or cyclohexanolis employed as a diluent, there is introduced an ingredient which exertsa solvent action on the paraflin component of the moisturepro'of layer.

We have also found that aromatic ketones, acyl aromatic ketones, andpolymethylene ketones, all of which are relatively high boilingcompounds may be usedas sealing agents with highly satisfactory results,and the production of strong, smooth seams. Among these may be mentionedcyclohexanone, acetophenone, and benzophenone, all of which are solventsfor cellulose acetate and ester gum but nonsolvents for paraffin. Withregard to the use of benzophenone, if this compound is applied inbenzene solution, and the latter evaporated it will behave more as aswelling agent than as a solvent, due to the diluent eifect of thebenzene. Cyclo hexanone and acetophenone are both liquids and may beused directly without the addition of other Benzophenone is a solid atordinary temperature, having a melting point of 48 C. and is preferablyapplied in solution in an appropriate solvent such as benzene.

The joints produced by the use of this com pound are extremely strong,and are found to be smoother than those produced with either of theother two compounds.

Other organic compounds of the type of the ether esters of the aromaticor aliphatic acids, also find use as sealing agents. A typical exampleof such compounds is ethoxy ethyl phthalate, a solid having a meltingpoint of approximately 285 C. This is a powerful swelling agent forcellulose acetate and dissolves ester gum but is a non-solvent withrespect to paraflin. This compound may best be applied from solution inbenzene, the latter being allowed to evaporate and leaving a thin filmof ether-ester on the surface of the moisture-proof sheets. The sheetsare then superimposed, and heat and pressure is applied. It should benoted, however, that butoxy ethyl phthalate is of limited compatabilitywith cellulose acetate. Methoxy ethyl phthalate is in about the samecategory as ethoxy ethyl phthalate.

Mixed ether alcohols have also been found to be effective when appliedto moistureproof sheeting according to the principles of our invention.For example, methoxy ethyl alcohol is a solvent for a wide variety ofcellulose acetates, a solvent for ester gum, and a non-solvent forparafiin. The ethoxy derivative is a strong swelling agent for celluloseacetate and at elevated temperatures this compound has a solvent actionthereon. Butoxy ethyl alcohol exertes a mild swelling effeet but is nota solvent for any cellulose acetates,

so far as at present known. Further, certain of the monoalkylderivatives of the polyhydric alcohols may be used. For example, bothmonoethyl and monobutyl ethers of ethylene glycol all gave good results.

We have also found that esters of the ether alcohols are suitable assealing agents. Both methoxy and ethoxy ethyl acetates are solvents forcellulose acetate, and ester gum, but nonsolvents for paramn. The butoxyderivative is a swelling agent for a variety of celluose acetatesroaaeoe' and, in some cases, is probably a solvent therefor.

With regard to the use of diluents with the above-mentioned compounds,this is governed largely by the amount of wax present in themoistureproof overcoating of the cellulosic sheet. If the overcoatinghas a relatively large amount of wax or consists of a wax layer laidover a gum layer, a sufficient proportion of diluent should be used togive the sealing agent solvent properties with respect to the wax inorder that it may penetrate the overcoating and exert its.characteristic solvent or swelling action on the adjacent underlyingportions of the base sheet. While we prefer to use toluene for thepurpose of dissolving the wax, we may employ benzol, xylol, cyclohexane,decane, octane, ethylene chloride, trichlorethylene, carbontetrachloride and other chlorinated or unchlorinated aliphatic oraromatic hydrocarbons.

It will, of course, be apparent in dealing with sealing agents which aresolids at ordinary temperatures that they are preferably brought to aliquid state before application, either by dissolving in a suitablesolvent, or by heating them to their melting temperatures.

As further illustrating the application of our process to the solventsealing of moistureproof cellulosic sheeting we include typical examplesof sealing operations carried out according to our invention, althoughit is to be understood that we are not limited to the particular detailstherein described.

Example I A tubular container similar to that shown in Fig. l is formedby folding a sheet of cellulose acetate having a thickness of the orderof .001 inch and having a moisture-proof overcoating of gum and wax tothe proper shape and applying to its edge portions a solution made up bydissolving -10% benzophenone in benzene. The edges of the sheets arethen brought together in the form of a joint and inserted between theelements 3 of Fig. 2 which are heated to a temperature of 120 to 145degrees centrigrade. An excellent smooth joint, free from blisters isthus produced.

Example II A container was made up from the same material as that usedin Example I, and the joint formed in the same manner, except thatbenzyl alcohol was used as the solvent.

Example III A package was made up from moisture-proof cellulosicsheeting and a joint produced by lapping the edge portions of the sheetone over the other after the application of a solution comprising ofethoxyethyl phthalate in benzene. Light pressure and a temperature ofabout 145 degrees centrigrade were applied and a clear transparent jointfree of wrinkles and blisters was produced.

As will be apparent from consideration of the compounds described above,the conditions of operation involved in their application will varyconsiderably. The control of temperature within certain limits isimportant.-

Although no hard and fast rule can be laid down, it may be said that themost satisfactory joints or seals are produced when the sealingtemperature is kept below the boiling point of the solvent and that, ingeneral the lower the boiling point'of the solvent, the lower should bethe temperature required to produce a clear. transparent seal free fromblistering. As a rule the higher the temperature, the greater will bethe tendency to blister with a given solvent sealing agent, although inmany cases a strong seal or joint may be produced, even where blisteringdoes occur, and where this defect is not important, exact control oftemperature will not be required. For most purposes we have found atemperature range of 120 to 145 C. to be satisfactory, althoughtemperatures considerably below 100 C., in some cases as low as 50 C. orlower, may be employed. Temperatures as high as 190 and in some caseshigher, give fairly satisfactory results in the case of the higherboiling solvents and where blistering is not a serious disadvantage. Inany event, the temperature should not be high enough to produce anundesirable softening of the cellulose acetate sheet itself, since thiswill cause stretching and consequent weakening of the sheet.

The pressure used to form the joints may also be varied to meet theparticular requirements of the material dealt with. The principalrequirement with respect to pressure is that it should provide a close,uniform contact of the treated surfaces of the sheets so that therespective moistureproof overcoatings and the softened portions of thebase material will coalesce to form a substantially uniform bond therebetween, but should not be high enough to cause wrinkling or otherundesirable deformation of the package.

The time of contact may be varied in accordance with the temperatureemployed and the volatility of the sealing agent, it, of course, beingapparent that the time required will be shorter in dealing with volatilecompounds than with those which are less volatile.

The requirements with respect to temperature, pressure and time ofcontact are largely matters of selection and will be apparent to thoseskilled in the art to which this invention relates. It will also beevident that many changes may be made in the details of carrying out ourinvention without departing from its spirit or scope. As a general rule,we prefer to use rather dilute solutions for our solvent sealingcompositions, since we have found that evaporation is more rapid and amore satisfactory thin film of adhesive material is deposited than isthe case with solutions of high concentration. We prefer a 510% solutionfor most types of joints, although we may employ more dilute solutionsthan 5% and, on the other hand, may use solutions containing much higherpercentages, especially if it is desirable to deposit as relativelythick film of adhesive agent.

The seams and closures produced according to the process of ourinvention are much stronger and more durable than those heretofore knownbecause of the fact that portions of cellulose acetate or othercellulosic material of which the base sheet may be composed merge withthe gumwax overcoating with the result that the joints are 'formed bothby the adhesive quality of the waterproofing layer and the comminglingof the underlying portions of the base material itself.

Although we have selected cellulose acetate as illustrating one type ofthin sheeting material which may be treated satisfactorily according toour invention, we do not intend to be limited thereby, since our processis equally applicable to other types of sheeting such as that producedfrom various other cellulose esters, including celluloseacetate-propionate, cellulose butyrate,

cellulose acetate-stearate, and. other mixed or simple esters ofcellulose.

Our invention is broadly applicable to the ers, display cartons, windowboxes, and many other articles requiring strong yet transparentclosures. It may also be employed to build up a laminated structurecomprised of a plurality of superimposed sheets or for applying abacking sheet of a given cellulosic material to another sheet of adifierent type and for many other purposes which will be apparent tothose skilled in the art.

What we claim as our invention and desire to secure by Letters Patent ofthe United States is:

1. The method of making a container which comprises forming a thin sheetof cellulosic material having an overcoating of gum and wax into thedesired shape, applying an organic solvent sealing agent to those edgesof the material which are to be joined in order to soften theovercoating and the adjacent underlying portions of the cellulosicmaterial, and pressing the treated edges together to join them and formthe container.

2. The method ofmaking a container which comprises forming a thin sheetof cellulosic material having an overcoating of. gum and wax into thedesired shape, applying an organic solvent sealing agent containing awax solvent to those edges of the material which are to be joined inorder to soften the overcoating and the adjacent underlying portions ofthe cellulosic material, and pressing the treated edges together to jointhem and form the container.

3. The method of making a container which comprises forming a thin sheetof cellulosic material having a gum-wax overcoating into the desiredshape, applying an organic solvent sealing agent containing a waxsolvent to the edges of the material to dissolve the overcoating and theadjacent underlying portions of the cellulosic material and pressing thetreated edges together at a temperature sufficient to evaporate off thesolvent mixture and to seal the sides and ends of the container.

4. The process of claim 3 wherein the solvent sealing agent is anoxygenated organic compound of the group consisting of the alcohols, thearomatic ketones, and organic esters.

5. The process of claim 3 wherein the solvent sealing agent is anaromatic alcohol.

6. The process of claim 3 wherein sealing agent is benzyl alcohol.

7. The process of claim 3 wherein the solvent sealing agent is anaromatic ketone.

8. The process of claim 3 wherein the solvent sealing agent isbenzophenone.

9. The process of claim 3 wherein the solvent sealing agent is anorganic ester.

10. The process of claim 3 wherein the solvent sealing agent is a mixedorganic ester.

11. The process of claim 3 wherein the solvent sealing agent is a mixedether-ester of an aromatic acid.

12. The process of claim 3 wherein the solvent sealing agent is a mixedether ester of phthalic acid.

13. The process of claim 3 wherein the solvent sealing agent is ethoxyethyl phthalate.

14. The methodof -making a sealed container which comprises forming athin sheet of cellulose the solvent I Leaaaoo acetate having amoistureproof gum-wax overcoating into the desired shape and in suchmanner that the edges of the sheet are brought together with theirrespective overcoa'ting layers in close proximity, applying a solventsealing agent comprising a solution of benzophenone in benzene to saidedges to dissolve the gum-wax coatings and adjacent portions of thecellulose acetate, and thereafter pressing them together at atemperature of 100-190 C. to evaporate ofi. the solvent.

15. The method of packaging articles of commerce which compriseswrapping them in a thin sheet of cellulosic material having amoistureproof gum-wax overcoating and sealing the package by treatingthe edges of the sheet with solvent sealing agent which is an oxygenatedorganic compound selected from the group consistclose proximity,applying a solvent sealing agent comprising a solution of ethoxy ethylphthalate in benzene to said edges to dissolve the gum-wax coatings andadjacent portions of the cellulose acetate and pressing them together ata tempera- .ture of 100-190" C. to evaporate off the solvent.

CYRIL J. STAUD. WILLIAM O. KENYON.

